Drill bit



DRILL BIT Filed June 4, 1935 INVENTOR Sylvesfer EMe/mrf' MTTO R N EYS til till

Sylvester Edward Mclnert, Nah, l2, asslgnor to Crucible Steel hem of erica, New York, N, Y., a corporation of New Jersey Application June 4, lath, Serial c. tidtl This invention pertains to improvements in drill bits adapted for drilling rock and the like, and more particularly to drill bits designed to he percussively driven and rotated.

An object of the invention is to provide a drill bit of the character referred to, wherein the cutting edges are so disposed and. of such configuration as to increase the rate and depth of cutting as compared to known types of drill bits for similar uses.

in the process of drilling the greatest amount of material to be removed is disposed adjacent the circumference of the bore, the material to be removed decreasing in amount toward the axis thereof. Accordingly, an efliciently constructed drill should have. its greatest cutting effectiveness adjacent its periphery.

0f the known types of rotary impact drill bits, some have wholly ignored this principle of design with resulting defects in use, whereas others, while recognizing and attempting to incorporate this principle, have either fallen short of or overshot the mark of most effective design. e results of comparative tests reveal that the present invention comes closer to the desired objective than the earlier constructions.

Of the known types of rotary impact drill bits, a familiar modification employs a plurality of radially projecting cutters, the cutting edges of which are substantially coplanar and perpendic ular to the axis of the bit. With this construction the cutting efiectiveness is the same at all distances from the bit axis and does not increase toward the periphery as is required for an emcient and lasting design. In conseuence the outer extremities of the cutters are worn away in process of drilling to a frustoconical contour, resulting in a progressive loss in gauge with depth of penetration and increased frictional resistance to rotation of the drill. i I! is not only'progressively decreases the rate of cutting with depth of penetration but ultimately causes the hit to become wedged or bound in the rock.

e attempt has been made to overcome this defect by providing the bit with radially pro iecting cutters in which all of the cutting edges are acutely inclined. to the s of the bit, whereby the outer extremities of the cutting edgesform with the circumferential faces of the cutters, a series of peripherallyarranged substantially coplanar sharp points projecting in the direction of the impact. The object of this is to increase the cutting action at the an; ference of the here where the material to be (cl. as

removed is greatest. This design has provw to he a swing too far in the opposite direction from that of the cutter first mentioned. Inasmuch as the sharp points must now equally assume the entire impact of the drill bit on the rock, they soon become blunted to such a degree that the cutting action is rendered negligible causing the bit thereby merely to pound in contrast to cutting the rock. Furthermore, with this construction penetration of the bit is greater at the periphery than at the center of the bore, so that the bottom of the hole assumes a convex contour, which by'increasing the frictional resistance to rotation causes the bit to wedge or bind.

it has been proposed further to provide rotary impact drill bits with a series of coplar radially disposed cutting edges alternating with other cutting edges extending circumferentiy adjacent the outer diameter. it has been observed that thls construction results in rapid loss of gauge causing the bit to bind.

According to the present invention it is proposed to enate the defects as noted in km tee of rotary impact drill bits, by providing the bit with a plurality of radially projecting cutting edges which are alternately perpendicular and acutely inclined to the axis of the bit, the outer extremities of the acutely inclined edges forming sharp cutting points which are preferably substantially coplanar with the cutting edges perpendicular to the axis of the bit. The cutters are preferably of substantially ll-section and terminate at their outer extreme ities adjacent the cutting edges in facets disposed in a substantially cylindrical surface cotill The observed superiority of this bit as regards speed of cutting, depth of penetration and life of the bit, results from the fact that the cutting edges perpendicular to the bit axis break away the material toward the center as well as at the periphery of the bore, and by assuming the major portion of the impact minimize wear on the cutting points of the oblique edges, the latter in turn by chipping out the material adjacent the circumference of the bore thus serving to mice loss of gauge and the tendency of the bit till to assume the' mentioned frusto-conical contour which would otherwise cause wedging. By imparting a proper obliquity to the inclined cutting edges, depending on the material to be cut, a proper balance may be maintained between eifectiveness of the aggregate cutting edge radially of the bit and the amount of material to be removed. In this way, all portions of the cutting edges are maintained at more nearly uniform effectiveness and more uniform wear accorded to the bit in process of cutting, than is the case with constructions heretofore known.

Referring to the drawing:

Fig. 1 shows in perspective a rotary impact drill bit according to a preferred form of the invention wherein the cutting edges radiate quadrantally from the axis of the bit;

Fig. 2 shows the bit of Fig. 1 in side elevation with the acutely inclined cutting edges illustrated in profile;

Fig. 3 is a plan view of the bit exposing the cutting edges to view;

Fig. 4 is a section along 4-4 of Fig. 3 showing in profile the cutting edges which are perpendicular to the bit axis; while Fig. 5 is a vertical section along 5-5 of Fig. 3 showing in profile the cutting edges which are acutely inclined to the bit axis.

In the drawing, the drill bit comprises a cylindrical shank l terminating at its lower extremity in the quadrantally positioned radially projecting cutters 2, 3, l, 5. The cutters '2, 3 have cutting edges 6, I, of substantially V-section, disposed in radial alignment substantially perpendicular to the axis 8-8 of the bit; while the cutters l, 5 have their cutting edges 9, I0, likewise of substantially V-section, disposed in radial alignment with the cutting edges acutely inclined to the bit axis 8-8, as shown more particularly in Figs. 2 and 5.

The cutters project as shown beyond the shank I, and terminate in substantially triangular facets H, [2, l3, H, the portions of these facets adjacent the cutting edges being disposed in a substantially cylindrical surface coaxial with the bit, and tapering inwardly therefrom and along the supporting ribs, such as l6, l1, l8, to the shank I.

As shown in Figs. 2, 4 and 5, the acutely inclined cutting edges 9, [0 are disposed axially of the bit in greater part between the shank and the level of the cutting edges 5, I which are perpendicular to the bit axis. Preferably, the outer extremities or points of the oblique cutting edges 9, in are substantially coplanar with the edges 6, l, the plane containing these portions being substantially perpendicular to the axis of the bit.

In the modification shown, the bit is screwthreadedly articulated to a drill rod I9, both the drill rod and the bit being axially bored at 20, 2|, respectively, for passage of compressed air or water serving to remove material loosened by the bit in the process of drilling. It will be understood, however, that the bit may be formed integral with the drill rod l9. In order to provide increased clearance, thereby to further facilitate the removal of material by means of water or compressed air forced through the bore 20, 2f, the bit is fluted longitudinally as at 23, 2 between the supporting ribs such as I6, I! and i8. Added clearance to this end is secured by the presence of the inclined cutting edges 9, l0.

when the bit is employed for rotary impact drilling, the sharp points at the outer extremities of the oblique cutters 8, Ill, serve to-loosen the material at the circumference of the bore and thereby to minimize loss of gauge with depth ofpenetration as well as the tendency of the bit to bind. The edges 8, I, perpendicular to the axis of the bit, out out the rock at the center as well as at the circumference of the hole, and by thus maintaining the bottom of the hole flush, further lessen the tendency of the bit to wedge or bind. Moreover, the perpendicular edges 6, l by assuming the major portion of the impact, protect the cutting points of the oblique edges.

The obliquity imparted to the cutting edges 9, H1 is governed somewhat by the hardness and character of the material to be drilled. By properly choosing the angle of obliquity 25, Fig. 5, the aggregate effectiveness of the cutting edges 9, It! can be so related to the cutting action of the perpendicularly disposed edges 8, I as to provide a desired increase in cutting effectiveness from the center to the outer extremity of the bit.

As illustrative of certain dimensions of a drill in accordance with the present invention which has proved highly eflective in use for drilling certain kinds of media, the angle of the obliquity 25, Fig. 5, of the cutting edges 8, [0 may be about I 4 degrees. The angle 28, Fig. 5, between the intersecting faces forming the V-section cutting edges, may be about degrees.

What I claim is:

1. A drill bit comprising: a shank terminating in a plurality of radially extending cutting edges of substantially equal radial extent, said cutting edges being disposed alternately substantially perpendicular and inclined to the axis of said bit, said perpendicular edges and the outer extremities of said inclined edges being substantially coplanar perpendicular to said axis, and the inner extremities of said inclined cutting edges being disposed axially of the bit closer to said shank than the outer extremities thereof.

2. A unitary drill bit comprising: a shank terminating in a plurality of radially extending cutters of V-section having cutting edges of substantially equal radial extent and allocation, said cutting edges being disposed alternately substantially perpendicular and inclined to the axis of said bit, said perpendicular edges and the outer extremities of said inclined edges being substantially coplanar perpendicular to said axis, and the inner extremities of said inclined cutting edges being disposed axially of said bit closer to said shank than the outer extremities thereof.

3. A unitary drill bit comprising: an axially apertured shank terminating in a plurality of radially extending cutters having cutting edges of V-section and of substantially equal radial extent, said cutting edges being disposed alternately substantially perpendicular and inclined to the axis of said bit, said perpendicular edges and the outer extremities of said inclined edges being substantially coplanar perpendicular to the bit axis, the inner extremities of said inclined edges being disposed axially of the bit closer to the shank than the outer extremities thereof, said cutters tapering inwardly from their outer extremities along supporting ribs integral with said shank.

4. A unitary drill bit comprising: an axially apertured shank terminating in a plurality of radially extending cutters having cutting edges of V-section and of substantially equal radial extent, said cutting edges being disposed alternately substantially perpendicular and inclined to the axis of said bit, said perpendicular edges and the outer extremities of said inclined edges being substantially coplanar perpendicular to the bit axis, the inner extremities of said inclined edges being disposed axially of the bit closer to the shank than the outer extremities thereof, said cutters terminating at their outer extremities in facets disposed in a substantially cylindrical surface, and tapering inwardly therefrom along supporting ribs integral with said shank, said shank being provided with flutings between said ribs for increased clearance.

5. A drill bit comprising: a shank terminating in quadrantally positioned radially extending cutting edges of substantially equal radial extent, said cutting edges being disposed alternately substantially perpendicular and inclined to the axis of said bit, said perpendicular edges and the outer extremities of said inclined edges being substantially coplanar perpendicular to said axis, and the inner extremities of said inclined edges being disposed axially of the bit closer to said shank than the outer extremities thereof.

6. A unitary drill bit comprising: a shank terminating in quadrantally positioned radially extending cutting edges of V-section and of substantially equal radial extent, said cutting edges being disposed alternately substantially perpendicular and inclined to the axis of said bit, said perpendicular edges and the outer extremities of said inclined edges being substantially coplanar perpendicular to said axis, and the inner extremities of said inclined axis being disposed axially of said bit closer to said shank than the outer extremities thereof.

7. A unitary drill bit comprising: an axially apertured shank terminating in quadrantally positioned radially extending cutters of equal radial extent having cutting edges of V-section disposed alternately substantially perpendicular and inclined to the axis of said bit, said perpendicular edges and the outer extremities of said inclined edges being substantially coplanar perpendicular to the bit axis, the inner extremities of said inclined edges being disposed axially of the bit closer to the shank than the outer extremities thereof, said cutters tapering inwardly from their outer extremities along supporting ribs integral with said shank.

8. A unitary drill bit comprising: an axially apertured shank terminating in quadrantally positioned radially extending cutters of equal radial extent having outing edges of V-section disposed alternately substantially perpendicular and inclined to the axis of said bit, said perpendicular edges and the outer extremities of said inclined edges being substantially coplanar perpendicular to the bit axis, the inner extremities of said inclined edges being disposed axially of the bit closer to the shank than the outer extremities thereof, said cutters terminating at their outer extremities in facets disposed in a substantially cylindrical surface, and tapering inwardly therefrom along supporting ribs integral with" said shank, said shank being provided with flutings between said ribs for increased clearance.

SYLVESTER EDWARD MEINERT. 

